Add matmtl_v2 to amp list (#28693)

* add matmtl_v2 to amp list

* support dygraph

python/paddle/fluid/contrib/mixed_precision/fp16_lists.py

@@ -74,6 +74,7 @@ class AutoMixedPrecisionLists(object):
 white_list = {
     'conv2d',
     'matmul',
+    'matmul_v2',
     'mul',
 }
 

python/paddle/fluid/dygraph/amp/auto_cast.py

@@ -27,6 +27,7 @@ __all__ = ['amp_guard']
 WHITE_LIST = {
     'conv2d',
     'matmul',
+    'matmul_v2',
     'mul',
 }